Chemical method of making a suspension, emulsion or dispersion of pyrithione particles

ABSTRACT

A method for producing a suspension, emulsion or dispersion of de-agglomerated particles (advantageously submicron-sized particles) of pyrithione salts comprising contacting agglomerated pyrithione salt particles with a de-agglomerating agent to produce the desired de-agglomerated pyrithione salt particles. Also disclosed is a method for making de-agglomerated submicron-sized particles of pyrithione salts comprision a heating step. Also disclosed are the particles made by the above methods and compositions comprising the particles and a base medium.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to methods for preparingparticles (advantageously submicron-sized particles) of pyrithionesalts, and, more specifically, to methods of preparing such particlesusing de-agglomeration procedures subsequent to production of theparticles. The present invention also relates to products made withthese particles.

[0003] 2. Description of the Related Art

[0004] Polyvalent metal salts of pyrithione (also known as1-hydroxy-2-pyridinethione; 2-pyridinethiol-1-oxide; 2 -pyridinethione;2 -mercaptopyridine-N-oxide; pyridinethione; and pyridinethione-N-oxide)are known to be effective biocidal agents, and are widely used asfungicides and bactericides in paints and personal care products such asanti-dandruff shampoos. The polyvalent metal salts of pyrithione areonly sparingly soluble in water and include magnesium pyrithione, bariumpyrithione, bismuth pyrithione, strontium pyrithione, copper pyrithione,zinc pyrithione, cadmium pyrithione, and zirconium pyrithione. The mostwidely used divalent pyrithione salts are zinc pyrithione and copperpyrithione.

[0005] Zinc and copper pyrithione are useful as antimicrobial agents andare active against gram-positive and negative bacteria, fungi, andyeasts. Zinc pyrithione is used as an antidandruff component inshampoos, while technical suspensions of zinc pyrithione and/or copperpyrithione are used as preservatives in paints and polymers. Synthesisof polyvalent pyrithione salts are described in U.S. Pat. No. 2,809,971to Berstein et al. Other patents disclosing similar compounds andprocesses for making them include U.S. Pat. Nos. 2,786,847; 3,589,999;3,590,035; 3,773,770.

[0006] Known methods for producing insoluble polyvalent salts ofpyrithione result in platelet-shaped (or other irregular shaped)particles having an average size greater than 1 micrometer (μm), andmore frequently in the range of 3 to 5 μm. These particles are eitherused directly, or can be converted into smaller particles. Smallerparticles of pyrithione salts (i.e., less than 1 micrometer or“submicron”) are often desired because they more easily formsuspensions, emulsions, or dispersions, and provide a larger surfacearea for enhanced biocidal activity. In addition, smaller particles,particularly in the low submicron range (e.g., below about 0.2 μm arebelieved to be semi-transparent to light, and below 0.1 μm will betransparent to light). This transparency provides the opportunity tomanufacture “clear” products, such as clear shampoos and soaps, that arepopular in the marketplace today, while providing the larger surfacearea desired for enhanced biocidal efficacy.

[0007] Submicron-sized particles of pyrithione salts are usuallygenerated by a separate mechanical manipulation step (e.g., grinding orcrushing) of larger particles or crystals that are made by conventionalprocesses. For example, European Patent Application No. 70046 describesa process for the preparation of zinc pyrithione using organic solvents.This process results in production of large crystals of zinc pyrithione.A separate, optional grinding step is used to grind the large crystalsand produce zinc pyrithione particles of smaller size. In anotherexample, U.S. Pat. No. 4,670,430 describes a process of making zincpyrithione particles with a median size of about 0.2 μm or less bymechanical grinding of larger particles of zinc pyrithione to thedesired submicron size. Unfortunately, mechanical grinding of largepyrithione particles into a submicron sized pyrithione particles tendsto not produce submicron-sized particles having a desired uniform size,shape and narrow particle size distribution. Such desired parameters areimportant since they are useful in rendering the behavior of theparticles in consumer products, such as shampoos and coatings,predictable. In addition, grinding generally results in substantial lossof useful product and is costly in terms of the equipment, time, andenergy required to provide the ground particles. Moreover, a desiredparticle shape for pyrithione particles, such as rods, needles, or othershapes with potentially enhanced biocidal activity, cannot easily beselected and produced by using grinding methodology.

[0008] Submicron-sized particles of pyrithione salts made by the methodsof the prior art also suffer from severe agglomeration in which many ofthe submicron-sized particles bond together through noncovalentinteractions to form larger particles of greater than 1 micron in size.Due to high mass, these large agglomerated particles tend to settle outof most consumer products over time and result in a hard packed layer ofpyrithione salt that is difficult to re-disperse.

[0009] What is needed in the art is a method for producingnon-agglomerated or de-agglomerated particles, advantageously having asubmicron size or larger, of pyrithione salts possessing a uniform size,shape and/or size distribution. Desirably, the particles, incorporatedinto a solution, suspension or dispersion, are stable against settlingout or agglomerate over time during shipping or storage prior to use. Inaddition, it is desired that the particles do not exhibit the damagethat is typically associated with mechanical grinding. The presentinvention is believed to provide answers to these needs.

SUMMARY OF THE INVENTION

[0010] In one aspect, the present invention relates to a method forproducing a suspension, emulsion, or dispersion of de-agglomerated(advantageously submicron-sized) particles of pyrithione salts,comprising contacting agglomerated pyrithione salt particles with ande-agglomerating agent, optionally in the presence of sonic energy, toproduce said suspension, emulsion, or dispersion of de-agglomeratedparticles of pyrithione salts.

[0011] In another aspect, the present invention provides a method formaking de-agglomerated submicron-sized particles of pyrithione saltscomprising the steps of:

[0012] a) filtering large particles of pyrithione salts having aparticle size in a range of from 1 to 50 microns to provide filteredparticles,

[0013] b) contacting the filtered particles with at least onede-agglomerating agent selected from the group consisting ofelectrolytes, surfactants, dispersants, and combinations thereof, toprovide a suspension or dispersion of de-agglomerated particles, and

[0014] c) heating said de-agglomerated particles to an elevatedtemperature of at least 60 degrees Centigrade in order to cause areduction in the size of the de-agglomerated particles to a submicronsize, thereby producing said de-agglomerated submicron-sized particlesof pyrithione salts.

[0015] In yet another aspect, the present invention relates to asuspension, emulsion, or dispersion of de-agglomerated pyrithioneparticles made by the above methods.

[0016] In yet another aspect, the present invention relates to apersonal care composition comprising at least one component selectedfrom the group consisting of shampoo, soap, skin care medicament, andcombinations thereof, and additionally comprising an antimicrobiallyeffective amount of de-agglomerated particles made by any of the abovemethods.

[0017] These and other aspects will become apparent upon reading thefollowing detailed description of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0018] It now has been surprisingly found, in accordance with thepresent invention, that a solution is provided to the problem ofproducing dispersions of nonagglomerated (advantageouslysubmicron-sized) particles of pyrithione salts. The present inventorshave solved this problem by treating particles of pyrithione salts madein a conventional manner with a deagglomerating agent that dispersesagglomerated pyrithione salt particles and forms a uniform dispersion ofsubmicron-sized particles of pyrithione salts that do not settle outover time. De-agglomerated particles produced in accordance with themethod of the present invention also display a narrow size distributionthat make them ideal for use in many consumer products, such asshampoos, coatings, and the like.

[0019] The present inventors have unexpectedly discovered thatagglomerated particles of pyrithione salts result in part fromnon-covalent molecular interactions, such as ionic attraction betweensmall particles, and that these non-covalent interactions can beneutralized by treating agglomerated particles made by prior art methodswith a de-agglomerating agent. For purposes of the present invention,the de-agglomerating agent may be a surfactant, an electrolyte, adispersant, or a combination of these. The method of the presentinvention produces a dispersion, suspension or emulsion comprisingparticles of pyrithione salts and having numerous advantages whenincorporated into personal care products, such as antidandruff shampoos,soaps, and the like. For example, a dispersion of submicron-sizedpyrithione salt particles possesses enhanced biocidal activity, relativeto such particles having a larger size, due to an increased surface areaper unit volume. In addition, the submicron-sized particles that aresuitably generated according to the method of the present invention donot re-agglomerate and remain homogeneously dispersed in solution.Prevention of re-agglomeration of the particles is particularlyimportant in the production of personal care products becauseagglomerated particles, or those that are prone to agglomerate, tend tosettle out over time and produce a dense layer of particles on thebottom of containers resulting in an unappealing product having limitedutility.

[0020] The present inventors have also surprisingly discovered thatapplication of heat (at a temperature s of at least 60 degreesCentigrade) to needle shaped pyrithione salt particles having particlesizes in the range of 1-50 microns causes the particles to decrease insize to the submicron range. This finding is particularly advantageoussince the needles are easily filtered to remove impurities, whereassubmicron-sized pyrithione salt particles are difficult to filter.Therefore, filtration of the needles, followed by de-agglomeration ofthe needles, and heating to produce the desired purified,submicron-sized particles should prove fruitful to the pyrithione saltsmanufacturing community.

[0021] As used herein, the term “submicron-sized particles” refers toparticles having an average diameter of less than one micron. The term“suspension, emulsion, or dispersion” is refers to a homogeneoussolution of particles that do not settle out or precipitate over time.The term “agglomerated pyrithione salt particles” refers to particles ofpyrithione salts that are bound together by non-covalent forces, such asionic interactions. The term “deagglomerated particles” refers toparticles that are not bonded together by non-covalent forces. The term“de-agglomerating agent” refers to any agent that neutralizes or reducesthe non-covalent forces in agglomerated particles.

[0022] The term “sonic energy” is broadly defined to encompass soundwaves in the audio sound spectrum, infrasound spectrum, and ultrasoundspectrum, preferably in the frequency range of from 20 Hz to 900,000 Hz(900 kHz) with power levels in the range from about 20 to about 5000watts, more preferably 100 to 1000 watts, most preferably 250 to 750watts, and is decibel (dB) levels from about 10 dB to about 180 dB,preferably 50 to 100 dB, most preferably 65 to 85 dB. The term“sonication”, as used herein, refers to application of sonic energy.

[0023] As used herein, the term “water-soluble salts of pyrithione” or“water-soluble pyrithione salts” include those salts of pyrithione inwhich the hydrogen atom of the thiol group is substituted with amonovalent cation. The term “water-soluble polyvalent metal salt” refersto those water-soluble salts in which the cation has a charge of +2 orgreater. The terms “particles of pyrithione salts” or “pyrithione saltparticles” as used herein refer to those salts of pyrithione that formprecipitates and are essentially insoluble or sparingly soluble in thesurrounding medium. The term “dispersant” as used herein refers to acompound that promotes uniform and maximum separation of extremely finesolid particles (i.e., colloidal size), and that does not promotefoaming.

[0024] An aspect of the present invention relates to a method fortreating agglomerated pyrithione salt particles made according to knownmethods with a de-agglomerating agent to produce a suspension, emulsion,or dispersion of particles (advantageously submicron-sized) particles ofpyrithione salts.

[0025] Pyrithione salt particles may be made by any process known in theart. In one embodiment, pyrithione or a water-soluble salt of pyrithioneis reacted with a water-soluble salt of a selected polyvalent metal inthe presence of a dispersant to form pyrithione salt particles as aprecipitate. Pyrithione in its acid form, or a water-soluble salt ofpyrithione may be used in the reaction. Useful water soluble salts ofpyrithione preferably include an ammonium ion or an alkali metal ionsuch as sodium. Accordingly, exemplary water soluble salts of pyrithioneinclude sodium pyrithione, potassium pyrithione, lithium pyrithione,ammonium pyrithione, and combinations of these. The most preferredwater-soluble salt of pyrithione useful in the present invention is thesodium salt (i.e., sodium pyrithione). The amount of pyrithione orwater-soluble salt of pyrithione can vary over a wide range andestablishing a useful amount is within the capabilities of the ordinaryskilled practitioner based on the stoichiometry of the reaction and therequired amount of particles that must be generated. A preferred amountof pyrithione or water-soluble pyrithione salt is from about 3% to about52% by weight of the total weight of the reaction mixture.

[0026] Exemplary water-soluble polyvalent metal salts useful inaccordance with the method of the invention include example zinc salts,tin salts, cadmium salts, copper salts, silver salts, zirconium salts,magnesium salts, aluminum salts, and the like. Combinations of thesesalts may also be employed. Useful counterions for these metals includenitrates, acetates, sulfates, halides or combinations thereof. Preferredwater-soluble polyvalent metal salts include zinc chloride (ZnCl₂) ,copper chloride (CuCl₂), zinc acetate (Zn(O₂CCH₃)₂) and zinc sulfate(ZnSO₄) . The amount of water-soluble polyvalent metal salt can varydepending on the amount of water-soluble salt of pyrithione. The molarratio of pyrithione or water-soluble salt of pyrithione to thewater-soluble polyvalent metal salt is generally in the range from about1:2 to about 1:8. Preferably, a slight stoichiometric excess (e.g., 5%of water-soluble polyvalent metal salt by weight over pyrithione orwater-soluble salt of pyrithione) is desirable to ensure a completereaction.

[0027] Useful media or carriers for the reaction include aqueous mediasuch as water, or water in combination with one or more organicsolvent(s). Useful organic solvents include alcohols, such as methanol,ethanol, amines such as diethanolamine, ether, esters, and the like.

[0028] Optional ingredients such as dispersants, surfactants, pearlizingagents (e.g., TiO₂-coated mica), and the like, may also be included inthe reaction mixture singly or in any combination. Exemplary dispersantsinclude salts of polymerized alkyl naphthalene sulfonic acids, such as“DARVAN 1” (sodium naphthalene sulfonic acid formaldehyde, a product ofR.T. Vanderbilt Co. Inc.), “DEMOL N” (sodium salt of naphthalenesulfonic acid, a product of Kao Chemicals), “DAXAD 11” (sodium salt ofpolymerized alkyl naphthalene sulfonic acids, a product of W.R. Grace &Co.), “TAMOL N” (sodium salt of condensed naphthalene sulfonic acid, aproduct of Rohm and Haas Co.), “HAROL KG” (potassium salts ofpolymerized alkyl naphthalene sulfonic acids, a product of GradenChemical Co.), “HAROL RG-71” (sodium salts of polymerized alkylnaphthalene sulfonic acids, a product of Graden Chemical Co.), “LOMARLS” (sodium salt of condensed mononaphthalene sulfonic acid, a productof Henkel Corp.) and the like.

[0029] Exemplary surfactants include nonionics, anionics, cationics, andamphoterics (the latter being also commonly referred to as“zwitterionics”). Nonionic surfactants include linear alcoholalkoxylates, such as the linear alcohol ethoxylates,ethyoxylated/propoxylated block copolymers, ethyoxylated/propoxylatedfatty alcohols, and polyoxyethylene cetyl ethers, and the like. Usefulanionic surfactants include alkyl diphenylether disulfonates, alkylphenyl ethoxylated phosphate esters, carboxylated linear alcoholalkoxylates, linear alkyl benzene sulfonic acid, diisobutylsulfosuccinate, alkyl sulfonates, and the like. Illustrative cationicsurfactants include alkyl triammonium halide, non-linear alkyl dimethylhalide, alkyl dimethyl benzyl ammonium halide-containing surfactants,and the like. Illustrative amphoteric surfactants include polyglycolether derivatives, ethoxylate oxazoline derivatives, lauramidopropylbetaine, lecithin, and the like.

[0030] Generally, these ingredients are utilized in the methods of thepresent invention in a pyrithione salt-dispersing effective amount,preferably an amount of from about 0.1 to about 20% by weight, morepreferably from about 0.1 to about 5% by weight, and most preferablyfrom about 0.1 to about 6% by weight, all based on the total weight ofthe reaction mixture.

[0031] The temperature of the reaction may be any temperature whichpermits precipitation of particles of pyrithione salt. Preferabletemperatures for the reaction are in the range of from between about 4and about 100° C., more preferably between about 25 and about 68° C.,and most preferably between about 30° C. and about 350° C.

[0032] In addition, the reaction may be gently agitated to promoteformation of the particles. Generally, gently stirring the reaction at150 rpm or less, and preferably about 100 rpm, after all the ingredientshave been combined is sufficient to promote formation of the particles.

[0033] Additional inorganic salts, such as potassium chloride, sodiumchloride, magnesium chloride, the corresponding sulfates, citrates,nitrates, and the like, may be added to the reaction medium to controlparticle length and shape. For example, suitable addition of salts canresult in particles of pyrithione salts having a variety of advantageousshapes, including nonspherical or non-platelet form, such as rods,needles, cylinders, cones, ellipsoids, prisms, parallelepipeds,pyramids, and the like. The particles formed by the present inventionmay also take the form of tetrahedrons, hexahedrons (cube), octahedrons,dodecahedrons, icosahedrons, and the like. The present inventors haveobserved that certain shapes of pyrithione salt particles offeradvantages of increase biocidal activity due to increased surface area.

[0034] Preferably, the additional salts are included in the reactionmixture from 0.1% by weight to about 10% by weight, more preferably fromabout 1% by weight to about 8% by weight, and most preferably from about3% by weight to about 6% by weight, all based on the total weight of thereaction mixture.

[0035] A particularly useful amount of additional sodium chloride addedto the reaction mixture to control particle size and shape is 5% byweight based on the total weight of the reaction mixture.

[0036] In one order to produce the elongated particles of the invention,pyrithione or a selected water-soluble salt of pyrithione and a selectedwater-soluble polyvalent metal salt are react ed in the presence of asurfactant or combination of surfactants in any suitable reaction vesselat a temperature below 70° C., and preferably between about 10° C. and68° C. In a preferred embodiment, sodium pyrithione is reacted with zincchloride or zinc sulfate in the presence of salt (e.g., sodium chloride)and a selected surfactant or combination of selected surfactants atabout 35° C. to form zinc pyrithione having rod or needles shapes, alongwith aqueous sodium chloride or aqueous sodium sulfate as by-products.The particles may also be utilized in a “continuous” process in whichthe zinc pyrithione particles are collected, and the mother liquorcontaining aqueous sodium chloride or sodium sulfate is recycled back tothe reaction vessel to provide a source of additional salt. An optionalfilter (e.g., carbon or charcoal filter) may be employed to removeimpurities such as colored organic compounds from the mother liquor.Particles of zinc pyrithione so formed have a “needle” or “rod”appearance. Generally, the rods or needles of zinc pyrithione saltproduced in accordance with the present invention are between about 0.1and about 1 μm in width and between about 2 and about 50 μm in length.Accordingly, the aspect ratio of the elongated particles is greater thanabout 1, and more preferably from about 2 to about 500.

[0037] The pyrithione salt particles may be isolated from the motherliquor by filtration, centrifugation, sedimentation, or other isolationmethods known in the art. Subsequent procedures, such as grinding, mayalso be performed. Alternatively, the agglomerated particles in thereaction medium may be treated with a deagglomerating agent directly.

[0038] During particle formation, either by the above exemplary methodor by other methods known in the art, the individual pyrithione saltparticles aggregate into larger agglomerates having sizes greater thanabout 1 micron. To reduce or eliminate this aggregation and to obtain apopulation of individual particles having sizes of less than 1 micron,the aggregated particles are treated with a deaglommerating agent toproduce a dispersion of submicron-sized particles of pyrithione salts.

[0039] The deagglomerating agent used in the method of the presentinvention may be any agent that separates agglomerated particles ofpyrithione salt. Examples of such deagglomerating agents includeelectrolytes, surfactants, sonic energy, and combinations of these. Theinventors have unexpectedly found that treatment of agglomeratedparticles with a deagglomerating agent neutralizes the noncovalentforces that result in agglomeration of the particles, and results inproduction of a population of pyrithione salt particles having sizes ofless than 1 micron.

[0040] Electrolytes used as a deagglomerating agent in the method of thepresent invention include alkali metal or alkaline earth metal salts(e.g., alkali metal or alkaline earth metal salts of chloride, sulfate,carbonate, citrate, benzoate), alkali metal or alkaline earth metaloxides, alkali metal or alkaline earth metal hydroxides, andcombinations thereof. Particularly useful electrolytes include sodiumchloride, calcium chloride, zince chloride, sodium oxide, calcium oxide,zinc oxide, sodium hydroxide, calcium hydroxide, and zinc hydroxide.Combinations of two, three, four, or more, of these electrolytes mayalso be used in accordance with the method of the present invention.

[0041] Preferably, electrolytes used according to the method of thepresent invention range from about 0.01 to 10% by weight, morepreferably, from about 0.1 to 5% by weight, and most preferably fromabout 0.5 to 3% by weight, based on the total weight containing theadmixture of aggregated particles (on a dry weight basis).

[0042] Dispersants useful in the present invention include salts ofpolymerized or unpolymerized alkyl naphthalene sulfonic acids. Usefulsalts of polymerized alkyl naphthalene sulfonic acids include “DARVAN 1”(sodium naphthalene sulfonic acid formaldehyde, a product of R.T.Vanderbilt Co. Inc.), “DEMOL N” (sodium salt of naphthalene sulfonicacid, a product of Kao Chemicals), “DAXAD 11” (sodium salt ofpolymerized alkyl naphthalene sulfonic acids, a product of W.R. Grace &Co.), “TAMOL N” (sodium salt of condensed naphthalene sulfonic acid, aproduct of Rohm and Haas Co.), “HAROL KG” (potassium salts ofpolymerized alkyl naphthalene sulfonic acids, a product of GradenChemical Co.), “HAROL RG71” (sodium salts of polymerized alkylnaphthalene sulfonic acids, a product of Graden Chemical Co.), “LOMARLS” (sodium salt of condensed mononaphthalene sulfonic acid, a productof Henkel Corp.) and the like.

[0043] Surfactants used as a deagglomerating agent in the method of thepresent invention anionic surfactants, cationic surfactants, nonionicsurfactants, amphoteric surfactants (also known as “zwitterionics”), andthe like.

[0044] Useful nonionic surfactants include linear alcohol alkoxylates,such as the linear alcohol ethoxylates, ethyoxylated/propoxylated blockcopolymers, ethyoxylated/propoxylated fatty alcohols, andpolyoxyethylene cetyl ethers, and the like. Useful linear alcoholalkoxylates are commercially available, for example, under theregistered trademark POLY-TERGENT SL-42, a product of Olin Corporation.If desired, the alcohol alkoxylate is suitably end-capped with a loweralkyl group, and such a product is commercially available asPOLY-TERGENT SLF-18, a propylene oxide-capped linear alcohol alkoxylatethat is also a product of Olin Corporation, and these end-capped linearalcohol alkoxylates are notably low foaming during use. Alsoadvantageous for use in accordance with the present invention aresurfactants within the group commercially available as POLY-TERGENTSLF-18B series surfactants, which are surfactants characterized byenhanced biodegradability (also products of Olin Corporation), beingalkene oxide-capped linear alcohol alkoxylates, containing ethyleneoxide moieties in the backbone, and suitably also containing at leastone propylene oxide moiety in the backbone, as disclosed, for example,in U.S. Pat. No. 4,925,587 and 4,898,621.

[0045] Other useful nonionic surfactants include one commerciallyavailable as NEODOL 91-6, a registered trademark surfactant product ofShell Chemical. This surfactant is a detergent range mixture ofC₉-C₁₁linear primary alcohol ethoxylates having an average of six molesof ethylene oxide per mole of alcohol. Other useful nonionic surfactantsinclude those is containing a linear C₉-C₁₁ carbon chain and five or sixethylene oxide or propylene oxide groups per molecule.

[0046] Useful anionic surfactants include alkyl diphenyletherdisulfonates, alkyl phenyl ethoxylated phosphate esters, carboxylatedlinear alcohol alkoxylates, linear alkyl benzene sulfonic acid,diisobutyl sulfosuccinate, and alkyl sulfonates. Useful anionics alsoinclude the alkylated diphenyl oxide sulfonates, and their methods ofpreparation are well-known, as illustrated by the disclosures of U.S.Pat. No. 3,264,242; 3,634,272; and 3,945,437, the disclosures of whichare all incorporated herein by reference. Commercial methods ofpreparation of the alkylated diphenyl oxide sulfonates generally do notproduce species which are monoalkylated, monosulfonated, dialkylated ordisulfonated. The commercially available species typically arepredominately (greater than 90 percent) disulfonated and are a mixtureof mono- and di- alkylated with the percentage of dialkylation beingabout 15 to about 25 percent, and the percentage of monoalkylation beingabout 75 to 85 percent. Most typically, the commercially availablespecies are about 80 percent is monoalkylated and 20 percentdialkylated.

[0047] Two illustrative commercially available solutions containingalkylated diphenyl oxide sulfonate surfactants are DOWFAX 8390 andDOWFAX 8390A surfactants, trademarked products of The Dow ChemicalCompany. In each, the alkyl group is predominantly a hexadecyl C₁₆group. These products are suitably employed in a solution fully orpartially neutralized with ammonium hydroxide if desired.

[0048] An advantageous anionic surfactant is also provided by reactingthe above-described alkylated diphenyl oxide sulfonates with apiperazine compound to produce a molar ratio of sulfonate compound topiperazine compound of between about 10:1 and about 1:10, preferablybetween about 2:1 and about 1:2. Although any piperazine compound can beused for such reaction, preferred compounds include those selected fromthe group consisting of 1,2-aminoethyl piperazine,1,4-piperazinediethane sulfonic acid, anhydrous piperazine, hydratedpiperazine, and combinations thereof.

[0049] Other useful anionics are polycarboxylated alcohol alkoxylates,preferably those selected from acids or organic or inorganic salts ofthe following: polycarboxylated linear alcohol alkoxylates,polycarboxylated branched alcohol alkoxylates, polycarboxylated cyclicalcohol alkoxylates, and combinations thereof. These polycarboxylatedalcohol alkoxylates typically contain at least two succinic acidradicals per molecule. Preferred polycarboxylated alcohol alkoxylatesare those having a backbone containing both poly(propylene oxide) andpoly(ethylene oxide) blocks, and such preferred polycarboxylated alcoholalkoxylates are readily commercially available, for example, asPOLY-TERGENT CS-1, a trademarked surfactant of Olin Corporation. Ifdesired, at least a portion of the acid groups on the polycarboxylatedalcohol alkoxylate are neutralized with a base to provide thecorresponding salt. Suitable bases include alkali metal hydroxides,alkaline earth metal hydroxides, and metal-free hydroxides, includingpotassium hydroxide, ammonium hydroxide, calcium hydroxide, magnesiumhydroxide, ammonia, mono-, di- and tri-ethanol amines, and combinationsthereof. Sodium hydroxide is preferred, and although potassium hydroxidecan be employed, it is not preferred. The organic or inorganic base ispreferably employed in at least an equimolar amount relative to thenumber of moles of polycarboxylated alcohol alkoxylated used. Thepolycarboxylated alcohol may also contain a polycarboxylic acid, forexample, polyacrylic acid, along with the starting alcohol alkoxylateand esters of the alkoxylate of the polycarboxylic acid.

[0050] Although individually the cationic and the amphoteric surfactantsare acceptable for use in the process of the present invention, they mayalso be used in combination with at least one surfactant from one of theother classes. Illustrative cationics include alkyl triammonium halide,non-linear alkyl dimethyl halide and alkyl dimethyl benzyl ammoniumhalide-containing surfactants. Illustrative amphoteric surfactantsinclude polyglycol ether derivatives, ethoxylate oxazoline derivatives,lauramidopropyl betaine, and lecithin.

[0051] Suitable blends can be employed in the process of the presentinvention based on various combinations of the above-describedsurfactants. Such a blend can be any combination of two or moresurfactants, between or within the above-described four broad classes ofsurfactants. Combinations can include blends of: anionic with anionic,anionic with nonionic, anionic with cationic, anionic with amphoteric,cationic with cationic, cationic with amphoteric, nonionic withnonionic, nonionic with amphoteric, and amphoteric with amphoteric.Likewise, ternary and quaternary blends of surfactants by selectingthree or four surfactants, respectively, from within or among theabove-described classes.

[0052] Suitably, any single or combination of two, three or foursurfactants from the following illustrative list are suitably employed:(a) nonionics, including alkoxylated linear alcohols (such asPOLY-TERGENT SLF-18 surfactant, a product of Olin Corporation), linearalcohol ethoxylates (such as NEODOL 91-8 surfactant, a product of theShell Corporation), ethoxylated linear alkyl benzene (such as TRITONX-100 surfactant, a product of Union Carbide Corporation), and EO/POblock copolymers (such as POLY-TERGENT E-17A surfactant, a product ofOlin Corporation); (b) anionics, including alkyl diphenyl etherdisulfonates (such as POLY-TERGENT 2A1 surfactant, a product of OlinCorporation), alkyl phenyl ethoxylated phosphate esters (such as WayfosM-60 surfactant, a product of Olin Corporation), carboxylated linearalcohol alkoxylates (such as POLY-TERGENT CS-1 surfactant, a product ofOlin Corporation), linear alkyl benzene sulfonic acid (such as BIOSOFTS-130 surfactant, a product of Stepan Company), alpha-olefin sulfonates(such as BIO TERG AS-40 surfactant, a product of Stepan Company),dialkylsulfosuccinates (such as AROWET SC-75 surfactant, a product ofArol Chemical Products), and alkyl sulfates (such as STEPANOL SLSsurfactant, a product of Stepan Company); (c) cationics including alkyltriammonium halides (such as CTAB surfactant, a product of VWRScientific Inc.), polyoxyethylene cocoamine (such as MAZEEN surfactant,a product of PPG Industries), primary alkyl amines (such as ARMEENsurfactant, a product of Akzo Chemical Co.), dicoco dimethyl ammoniumhalide (such as JET QUAT surfactant, a product of Jetco Chemical Inc.),di-isodecyl dimethyl ammonium halides (such as AMMONYX K9 surfactant, aproduct of Stepan Company), and diethyl aminoethyl stearate (such asCERASYNT 303 surfactant, a product of ISP Van Dyke); and, (d)amphoterics, including polyglycol ether derivatives (such as ALBEGAL Asurfactant, a product of Ciba-Geigy), ethoxylated oxazolin derivatives(such as ALKATERG T-IV surfactant, a product of Angus Chemicals),lauramide propyl betain (such as LEXAINE C surfactant, a product ofInolex Chemicals), lecithin (such as CANASPERSE surfactant, a product ofCan Amoral), disocium cocoamphodiacetate (such as MONATERICS surfactant,a product of Mona Industries), complex fatty amine salt (such as MAFO 13surfactant, a product of PPG Industries), and cocoamine oxide (such asMACKAMINE CO surfactant, a product of the McIntyre Group Ltd.).Combinations of two, three, four, or more, of these surfactants may alsobe used in accordance with the method of the present invention.

[0053] Preferably, surfactants used according to the method of thepresent invention range from about 0.01 to 10% by weight, morepreferably, from about 0.025 to 5% by weight, and most preferably fromabout 0.05 to 1% by weight, based on the total weight of the admixturecontaining aggregated particles (on a dry weight basis).

[0054] Sonic energy is optionally employed in the methods of the presentinvention in order to facilitate or expedite the desiredde-agglomeration being effected by the de-agglomerating agent(s), and toenhance the uniformity of the resulting suspension, dispersion oremulsion. If used, the sonic energy is preferably applied to theagglomerated pyrithione salt particles in the presence of thede-agglomerating agent(s) to form a highly uniform suspension ofnon-agglomerated particles. The sonic energy preferably has a frequencyof from about 20 Hz to about 900,000 Hz (900 kHz), more preferably fromabout 5 kHz to about 105 kHz, and most preferably from about 16 kHz toabout 20 kHz. Combinations of frequencies may also be used, depending onthe configuration of the particular sonication apparatus. The energylevel output that results from the sonic energy applied to the reactionmixture is preferably in the range from about 20 to about 5000 Watts,more preferably from about 100 to about 1000 Watts, and most preferablyfrom about 400 to about 600 Watts. An example of a suitable sonicationdevice that is useful according to the method of the invention is aNearfield NAP Model 3606 acoustical processor (available commerciallyfrom Advanced Sonic Processing Systems, Woodbury, Conn.), although anysonication device may be employed in the method of the invention.

[0055] It will be noted that the sound levels that could be producedusing the levels of sonic energy discussed above can exceed 100 decibels(dB) and potentially reach levels as high as 140 dB. In order to avoidhearing impairment, proper safety and sound abatement procedures shouldbe undertaken when decibel levels are greater than about 80 dB.

[0056] Preferably, in the batch process, sonic energy is applied to thereaction mixture through a climate probe that is placed in directcontact with the particles after their formation. Other methods ofapplying sonic energy are also feasible, such as a pipe which carriesthe sonic energy to the reaction vessel, or a chamber lined with sonicenergy transducers. The latter method is particularly useful in thecontinuous manufacture of particles as described in copending U.S.patent application Serial No. (Attorney Docket No. 101715-100, filed onFeb. 23, 1999), incorporated herein by reference in its entirety.

[0057] The uniform, well-dispersed suspension of non-agglomeratedparticles made according to the method of the invention is useful in theproduction of personal care products (e.g., shampoos, soaps, etc.),cleaning products, paints, coatings, foodstuffs, fertilizers, poolchemicals, foodstuffs, and the like. For example, deagglomerated zincpyrithione particles made according to the method of the invention are auseful component of antimicrobial-containing shampoos, e.g., as anantidandruff additive in providing an antidandruff efficacycharacteristic to shampoos. Generally, the antimicrobial-containingpersonal care composition of the present invention may contain any “basemedium” component found in shampoos, soaps, or skin care medicaments,such as, for example, glycerine, aloe, surfactants such asdodecyl-benzene sulfonate (“DDBS”), mineral oil, water, and combinationsthereof. Other such components are described in the examples providedhereinbelow.

[0058] The following examples are intended to illustrate, but in no waylimit the scope of the present invention. All parts and percentages areby weight and all temperatures are in degrees Celsius unless explicitlystated otherwise. In the following Examples “q.s.” means quantitysufficient, generally 0.1 to 2% by weight.

EXAMPLES Example 1

[0059] Production of Needles of Zinc Pyrithione

[0060] To a 1200 g of 6% sodium pyrithione solution was added 6.0 g ofdispersant (sodium salt of polymerized alkyl naphthalene sulfonic acidsold under the tradename DARVAN 1 available from J.T. Vanderbilt) in a3000 ml jacketed cylindrical pyrex reactor. The temperature was raisedto 35° C. and maintained throughout the reaction sequence. 437 g of a10% aqueous zinc sulfate monohydrate solution was pumped into thereactor over 50 to 60 minutes using a peristaltic pump. The productslurry was isolated by filtration with a Buchner funnel and washed withwater.

[0061] Upon analysis, the isolated reaction product was about 19.6% zincpyrithione by weight. Under microscopic examination, the isolatedproduct was found to consist of particles of zinc pyrithione having rodor needle shape.

Example 2

[0062] Production of Needles of Zinc Pyrithione

[0063] A solution of 355 g of 16.9% by weight sodium pyrithione, 845 mlwater, and 2.4 g of DARVAN 1 (sodium naphthalene sulfonic acidformaldehyde) was placed in a 2000 ml jacketed reaction vessel andwarmed to 39° C. A solution of 198.5 g of 20% by weight zinc sulfatemonohydrate and 595.4 ml water was added over about 68 minutes.Following addition of the zinc sulfate solution, the mixture was stirredfor 20 minutes and the product was isolated by filtration and washed.The isolated precipitate was assayed and found to contain about 33.6% byweight zinc pyrithione.

[0064] The zinc pyrithione particles were resuspended in an aqueoussolution of water and DARVAN 1 (sodium naphthalene sulfonic acidformaldehyde) to form solution containing 25% by weight zinc pyrithioneand 0.1% by weight DARVAN 1 dispersant. The particles were analyzed on aHoriba 910 Particle Size Analyzer. Photomicrographs showed that theparticles had an elongated form and appeared as rods or needles. Thewidth of the rods and needles varied from about 0.1 to about 1 μm, andthe length of the rods and needles varied from about 2 to about 10 μm.Repeated particle size analysis of this product using the Horiba 910Analyzer over time (i.e, during several days of measurement) indicatedthat the particle size distribution did not change. Hence, theagglomerates had been removed, and re-agglomeration did not reoccur.

Example 3

[0065] De-agglomeration of Agglomerated Zinc Pyrithione Particles.

[0066] 1000 g of 25% aqueous solution of zinc pyrithione particles madein accordance with the protocol of Examples 1 and 2 above were pouredinto a 2 L beaker. 1 gram of DARVAN 1 dispersant and 1 gram of calciumchloride were added respectively to the beaker and mixed with a handmixer for 1-2 minutes at high speed. The contents are then transferredto a 2 liter glass jacketed reactor and gently mixed at about 150 rpmusing Lithinin A320 blades. The reactor was heated to about 65° C. andheld for approximately 15 minutes. Chloroisothiazolone was added as apreservative to a final concentration of approximately 3 ppm duringheating. Approximately 3 minutes after addition of the preservative, theheat is turned off and the mixture is allowed to cool to roomtemperature. The particles are then transferred to a storage containerand analyzed over several days for size, dispersion, color, settlementand agglomeration. The particle size distribution did not change over aperiod of several days (as shown by repeated measurements of the productusing a Horiba 910 Particle Size Analyzer), thus demonstrating that theparticles did not re-agglomerate over time.

Example 4

[0067] Deagglomeration of Agglomerated Zinc Pyrithione Particles.

[0068] 1000 g of 25% aqueous solution of zinc pyrithione particles madein Example 1 or 2 above were poured into a 2 L beaker. 0.5 gram ofWITCAMIDE 5130 series surfactant, an alkanolamide nonionic surfactant ofWitco Chemicals, and 10 grams of sodium chloride were added respectivelyto the beaker and mixed with a hand mixer for 1-2 minutes at high speed.The contents are then transferred to a 2 liter glass jacketed reactorand gently mixed at about 150 rpm using Lithinin A320 blades. Thereactor was heated to about 65° C. and held for approximately 15minutes. Methylisothiazolone was added as a preservative to a finalconcentration as needed (approximately 3 ppm) during heating.Approximately 3 minutes after addition of the preservative, the heat isturned off and the mixture is allowed to cool to room temperature. Theparticles are then transferred to a storage container and analyzed overseveral days for size, dispersion, color, settlement, and agglomeration.Again, for this product the particle size distribution did not changeover a period of several days (as shown by repeated measurements of theproduct using a Horiba 910 Particle Size Analyzer), thus demonstratingthat the particles did not re-agglomerate over time.

Example 5 (Proposed Example)

[0069] Antidandruff Shampoo Formulation I

[0070] An antidandruff shampoo composition is made using de-agglomeratedparticles of zinc pyrithione, prepared as described in Examples 1-4, incombination with the following ingredients: Component A: Water 41.0%Magnesium aluminum silicate 1.0% Hydroxypropyl methylcellulose 0.8%Component B: Zinc Pyrithione (25% aqueous dispersion) 4.0% Component C:Cocamide DEA 1.0% Component D: Triethanolamine lauryl sulfate, 40% 40.0%Triethanolamine, 99% 3.2% FD&C Blue No. 1 (0.2%) 1.5% FD&C Yellow No. 5(0.1%) 0.5% Fragrance q.s.

[0071] The antidandruff shampoo composition is made as follows:

[0072] Component A is prepared by heating water to 70° C. and dissolvingthe other two components with stirring (about 1500 rpm). Component B isadded, and stirring continued for 5 minutes. Stirring speed was reducestirring to ˜300 RPM. Component C is melted in a separate container, andadded to the A/B mixture. The heat is removed and component D is addedwhile the mixture cooled.

Example 6 (Proposed Example)

[0073] Antidandruff Shampoo Formulation II

[0074] Another antidandruff shampoo composition is made using zincpyrithione made as described in Examples 1-4 in combination with thefollowing ingredients: Component A: Deionized water q.s. Ammonium laurylsulfate 15.0% Cocamide DEA 2.0% Component B: Di (hydrogenated) tallowphthalic 5.0% acid amide Zinc Pyrithione (25% aqueous dispersion) 4.0%Component C: Preservative q.s. Component D: Citric Acid, 50% aq.Solution, OR q.s. Sodium hydroxide, 50% aqueous solution Component E:Ammonium chloride q.s.

[0075] The antidandruff shampoo composition is made as follows:

[0076] In separate containers, components A and B are each mixed well.Component A is heated to 165-170° F. and component B is added. Themixture is stirred for 30 minutes. The mixture is then cooled to 120°F., and component C was added. The pH of the resulting mixture isadjusted to 5.0-6.2 with component D, and the viscosity is adjusted withcomponent E.

Example 7 (Proposed Example)

[0077] Antidandruff Shampoo with Conditioner I

[0078] An antidandruff shampoo and conditioner composition is made usingneedle and rod forms of zinc pyrithione made as described in Examples1-4 in combination with the following ingredients: Component A:Deionized Water q.s. Ammonium lauryl sulfate 20.0% Cocamide DEA 2.0%Component B: Di (hydrogenated) tallow phthalic 4.0% acid amide ZincPyrithione (25% aqueous dispersion) 4.0% Dimethicone, 12,000 cps 0.5%Component C: Preservative q.s. Component D: Citric acid, 50% aqueoussolution, OR q.s. Sodium hydroxide, 50% aqueous solution Component E:Ammonium chloride q.s.

[0079] The antidandruff shampoo and conditioner composition is made asfollows:

[0080] In separate containers, components A and B is each mixed well.Component A is heated to 165-170° F. and component B is added. Themixture is stirred for 30 minutes. The mixture is then cooled to 120°F., and component C was added. The pH of the resulting mixture isadjusted to 5.0-6.2 with component D, and the viscosity is adjusted withcomponent E.

Example 8 (Proposed Example)

[0081] Antidandruff Shampoo with Conditioner II

[0082] Another antidandruff shampoo and conditioner composition is madeusing needle and rod forms of zinc pyrithione made as described inExamples 1-4 in combination with the following ingredients: Component A:Deionized water q.s. Guar hydroxypropyl trimonium chloride 0.30%Magnesium Aluminum Silicate 0.70% Zinc Pyrithione (25% aqueousdispersion) 4.0% Component B: Sodium laureth sulfate 30.0% Ammoniumxylene sulfonate, 40% aq. 02.0% Component C: Tricetylammonium chloride0.50% Cetyl alcohol NF 0.40% Stearyl alcohol 0.40% Glycol distearate2.00% Component D: Cocamide MEA 1.70% Ammonium lauryl sulfate 36.00%Component E: Preservative 0.05% Fragrance and dye q.s. Component FCitric acid, 25% aqueous solution q.s.

[0083] The antidandruff shampoo and conditioner composition is made asfollows:

[0084] Component A is prepared by heating water to 50° C. and dispersingthe guar hydroxypropyl trimonium chloride and the magnesium aluminumsilicate with rapid agitation. The zinc pyrithione dispersion is addedto this combination with stirring. The pH of component A is adjusted to4.5-5.0 with component F. Both components of B are slowly added tocomponent A, mixing well. The pH of the mixture is adjusted to 5.7-6.3with component F. In a separate container, component C is heated to70-75° C. The A/B mixture is heated to 70-75° C. and blend withcomponent C, mixing well. Both components of D are added to the hotmixture, and stirred well. The pH of the mixture are adjusted to 5.7-6.3with component F. The mixture is cooled to 40-45° C., and component Ewas added with stirring. If a higher viscosity is desired, adding0.05-1% sodium chloride can increase the viscosity of the product.

Example 9 (Proposed Example)

[0085] “Extra Body” Antidandruff Shampoo

[0086] An “extra body” antidandruff shampoo and conditioner compositionis made using needle and rod forms of zinc pyrithione made as describedin Examples 1-4 in combination with the following ingredients: ComponentA: Deionized Water q.s. Zinc Pyrithione (25% aqueous dispersion) 4.0%Component B: Methyl Paraben 0.30% Propyl Paraben 0.10% Propylene Glycol0.50% Sodium Chloride 0.50% Component C: Triethanolamine lauryl sulfate20.0% Cocamide MEA 4.0% Ethylene glycol distearate 7.0% Component D:Cocodimonium hydrolyzed animal protein 1.00% Component E: FD&C Blue No.1 q.s. Component F: Citric Acid, 50% aqueous solution q.s.

[0087] The antidandruff shampoo and conditioner composition are made asfollows:

[0088] Component A is heated to 70° C. The ingredients of component Bare added with good stirring until dissolved. The ingredients ofcomponent C are added to the mixture sequentially, and heated withmixing to 75° C. The mixture is cooled with stirring to 40° C., andcomponents D and E are added with stirring. The pH of the finalcomposition is adjusted to 4.7 with component F.

[0089] Although the invention has been shown and described with respectto illustrative embodiments thereof, it should be appreciated that theforegoing and various other changes, omissions and additions in the formand detail thereof may be made without departing from the spirit andscope of the invention as delineated in the claims. All patents andpatent applications mentioned are herein incorporated by reference intheir entireties.

What is claimed is:
 1. A method for producing a suspension, emulsion, ordispersion of de-agglomerated particles of pyrithione salts, comprisingcontacting agglomerated pyrithione salt particles with ande-agglomerating agent, optionally in the presence of sonic energy, toproduce said suspension, emulsion, or dispersion of de-agglomeratedparticles of pyrithione salts.
 2. The method of claim 1, wherein saiddeagglomerating agent is selected from the group consisting ofelectrolytes, surfactants, dispersants, and combinations thereof.
 3. Themethod of claim 2, wherein said electrolyte is selected from the groupconsisting of alkali metal or alkaline earth metal salts, alkali metalor alkaline earth metal oxides, alkali metal or alkaline earth metalhydroxides, and combinations thereof.
 4. The method of claim 3, whereinsaid electrolyte is an alkali metal or alkaline earth metal salt ofchloride, sulfate, carbonate, citrate, benzoate, and combinationsthereof.
 5. The method of claim 4, wherein said electrolyte is selectedfrom the group consisting of sodium chloride, calcium chloride, zincchloride, sodium oxide, calcium oxide, zinc oxide, sodium hydroxide,calcium hydroxide, zinc hydroxide, and combinations thereof.
 6. Themethod of claim 2, wherein said electrolyte is present in saidsuspension, emulsion or dispersion in and amount of from about 0.01 to10% by weight, based on the total weight of said admixture.
 7. Themethod of claim 6, wherein said electrolyte is present in said admixtureof agglomerated pyrithione salt particles from about 0.1 to 5% byweight, based on the total weight of said admixture.
 8. The method ofclaim 7, wherein said electrolyte is present in said admixture ofagglomerated pyrithione salt particles from about 1 to 3% by weight,based on the total weight of said admixture.
 9. The method of claim 2,wherein said surfactant is selected from the group consisting of saltsof anionic surfactants, cationic surfactants, nonionic surfactants,amphoteric surfactants, and combinations thereof.
 10. The method ofclaim 2, wherein said dispersant is a salt of polymerized orunpolymerized alkyl naphthalene sulfonic acids.
 11. The method of claim1, wherein said sonic energy is employed and wherein said sonic energyhas a frequency of from about 20 Hz to about 900 kHz.
 12. The method ofclaim 11, wherein said sonic energy has a frequency of from about 5 kHzto about 105 kHz.
 13. The method of claim 12, wherein said sonic energyhas a frequency of from about 16 kHz to about 20 kHz.
 14. The method ofclaim 2, wherein said sonic energy has an energy level of from about 20to about 5000 Watts.
 15. The method of claim 14, wherein said sonicenergy has an energy level of from about 100 to about 1000 Watts. 16.The method of claim 15, wherein said sonic energy has an energy level offrom about 400 to about 600 Watts.
 17. The method of claim 1, whereineach of said particles of pyrithione salts has a size within a range offrom 0.01 to 50 microns.
 18. The method of claim 1, wherein saidadmixture of agglomerated pyrithione salt particles is made by reactingpyrithione or a water-soluble salt of pyrithione and a water-solublepolyvalent metal salt in a carrier and in the presence of a dispersantat a temperature from about 4° C. to about 100° C. to produce anadmixture of agglomerated pyrithione salt particles.
 19. The method ofclaim 18, wherein said water-soluble salt of pyrithione is selected fromthe group consisting essentially of sodium pyrithione, potassiumpyrithione, lithium pyrithione, ammonium pyrithione, and combinationsthereof.
 20. The method of claim 18, wherein said water-solublepolyvalent metal salt is a divalent salt selected from the groupconsisting essentially of zinc salts, tin salts, cadmium salts, coppersalts, silver salts, zirconium salts, magnesium salts, aluminum salts,nitrate salts, acetate salts, sulfate salts, halide salts, andcombinations thereof.
 21. The method of claim 20, wherein said divalentsalt is selected from the group consisting essentially of zinc sulfate,zinc chloride, zinc acetate, copper chloride, and combinations thereof.22. The method of claim 18, wherein said dispersant is selected from thegroup consisting essentially of sodium salts of polymerized alkylnaphthalene sulfonic acids and combinations thereof.
 23. The method ofclaim 1, wherein said submicron-sized particles of pyrithione salt havea form selected from the group consisting essentially of rods, needles,cylinders, cones, ellipsoids, prisms, parallelepipeds, pyramids,tetrahedrons, hexahedrons (cube), octahedrons, dodecahedrons,icosahedrons, and combinations thereof.
 24. The method of claim 1,further comprising the step of isolating said agglomerated particles ofpyrithione salt.
 25. A suspension, emulsion or dispersion ofdeagglomerated submicron-sized pyrithione particles made by the methodof claim
 1. 26. An antidandruff shampoo composition comprising thesuspension, emulsion or dispersion of deagglomerated submicron-sizedparticles of pyrithione salts made by the method of claim
 1. 27. Amethod for making de-agglomerated submicron-sized particles ofpyrithione salts which comprises the steps of: a) filtering largeparticles of pyrithione salts having a particle size in a range of from1 to 50 microns to provide filtered particles, b) contacting thefiltered particles with at least one de-agglomerating agent selectedfrom the group consisting of electrolytes, surfactants, dispersants, andcombinations thereof, to provide a suspension or dispersion ofde-agglomerated particles, and c) heating said de-agglomerated particlesto an elevated temperature of at least 60 degrees Centigrade in order tocause a reduction in the size of the de-agglomerated particles to asubmicron size, thereby producing said de-agglomerated submicron-sizedparticles of pyrithione salts.
 28. The method of claim 27 wherein thelarge particles of step a) are in the form of needles.
 29. A personalcare composition comprising at least one component selected from thegroup consisting of shampoo, soap, skin care medicament, andcombinations thereof, and additionally comprising an antimicrobiallyeffective amount of de-agglomerated particles made by the method ofclaim
 1. 30. A personal care composition comprising at least onecomponent selected from the group consisting of shampoo, soap, skin caremedicament, and combinations thereof, and additionally comprising anantimicrobially effective amount of de-agglomerated particles made bythe method of claim 27.